/**
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright (c) 2007 Sun Microsystems Inc. All Rights Reserved
*
* The contents of this file are subject to the terms
* of the Common Development and Distribution License
* (the License). You may not use this file except in
* compliance with the License.
*
* You can obtain a copy of the License at
* https://opensso.dev.java.net/public/CDDLv1.0.html or
* opensso/legal/CDDLv1.0.txt
* See the License for the specific language governing
* permission and limitations under the License.
*
* When distributing Covered Code, include this CDDL
* Header Notice in each file and include the License file
* at opensso/legal/CDDLv1.0.txt.
* If applicable, add the following below the CDDL Header,
* with the fields enclosed by brackets [] replaced by
* your own identifying information:
* "Portions Copyrighted [year] [name of copyright owner]"
*
* $Id: HeadTaskRunnable.java,v 1.4 2008/06/25 05:52:51 qcheng Exp $
*
*/
package com.sun.identity.common;
import java.util.Date;
import java.util.Set;
/**
* HeadTaskRunnable is designed to be the head of the linked-list when
* TaskRunnable needs to be linked together. Whenever there is an insertion or
* deletion, HeadTaskRunnable must be locked to guarantee correct
* synchronization. Besides, when last element of the linked-list is removed
* (setNext(null)), HeadTaskRunnable should use Triggerable to remove or destroy
* the linked-list.
*/
public class HeadTaskRunnable implements TaskRunnable {
protected Date time;
protected volatile TaskRunnable nextTask;
protected volatile TaskRunnable tailTask;
protected volatile boolean expired;
protected volatile boolean timeout;
protected int waitCount;
protected int acquireCount;
protected volatile Thread owner;
protected Triggerable parent;
/**
* Constructor of HeadTaskRunnable.
*
* @param parent The Triggerable interface to be run when the linked-list is
* empty
* @param nextTask The TaskRunnable next to this TaskRunnable
* @param time The time this TaskRunnable is scheduled
*/
public HeadTaskRunnable(Triggerable parent, TaskRunnable nextTask,
Date time) throws IllegalArgumentException {
if ((time == null) || (nextTask == null)) {
throw new IllegalArgumentException();
}
this.time = time;
this.owner = null;
this.nextTask = nextTask;
this.tailTask = nextTask;
this.expired = false;
this.timeout = false;
this.waitCount = 0;
this.acquireCount = 0;
this.nextTask.setHeadTask(this);
this.nextTask.setPrevious(this);
this.parent = parent;
}
/**
* Sets the status of the HeadTask to expired.
*/
protected synchronized void expire() throws IllegalMonitorStateException {
if (owner == Thread.currentThread()) {
expired = true;
} else {
throw new IllegalMonitorStateException(
"The calling thread is not the owner of the lock!");
}
}
/**
* Sets the status of the HeadTask to timeout.
*/
protected synchronized void timeout() throws IllegalMonitorStateException {
if (owner == Thread.currentThread()) {
timeout = true;
} else {
throw new IllegalMonitorStateException(
"The calling thread is not the owner of the lock!");
}
}
/**
* Returns a boolean to indicate whether the HeadTask is timeout already.
*
* @return a boolen to indicate whether the HeadTask is timeout.
*/
public boolean isTimedOut() {
return timeout;
}
/**
* Returns a boolean to indicate whether the HeadTask is expired already.
*
* @return a boolean to indicate whether the HeadTask is expired.
*/
public boolean isExpired() {
return expired;
}
/**
* Returns the thread which currently holding this lock.
*
* @return the thread which currently own the lock or null.
*/
public Thread getCurrentOwner() {
return owner;
}
/**
* Tries to acquire a valid (non-expired) lock.
*
* @return a boolean to indicate whether it is succeed to acquire the lock.
*/
public synchronized boolean acquireValidLock() {
while (!expired) {
if (owner == null) {
owner = Thread.currentThread();
acquireCount = 1;
return true;
} else {
if (owner != Thread.currentThread()) {
try {
waitCount++;
this.wait();
waitCount--;
} catch (InterruptedException ex){
//ignored
}
} else {
acquireCount++;
return true;
}
}
}
return false;
}
/**
* Releases the currently holding lock.
*/
public synchronized void releaseLockAndNotify() throws
IllegalMonitorStateException {
if (owner == Thread.currentThread()) {
if (acquireCount > 1) {
acquireCount--;
} else {
owner = null;
acquireCount = 0;
if (waitCount > 0) {
if (expired) {
this.notifyAll();
} else {
this.notify();
}
}
}
} else {
throw new IllegalMonitorStateException(
"The calling thread is not the owner of the lock!");
}
}
/**
* Implements for TaskRunnable interface, no actual use for HeadTaskRunnable.
*/
public void setHeadTask(HeadTaskRunnable headTask) {
}
/**
* Implements for TaskRunnable interface, no actual use for HeadTaskRunnable.
*/
public HeadTaskRunnable getHeadTask() {
return null;
}
/**
* Implements for TaskRunnable interface, always return false.
*
* @return false means nothing can be added to this TaskRunnable
*/
public boolean addElement(Object key) {
return false;
}
/**
* Implements for TaskRunnable interface, always return false.
*
* @return false means nothing can be removed from this TaskRunnable
*/
public boolean removeElement(Object key) {
return false;
}
/**
* Implements for TaskRunnable interface, always return false.
*
* @return true means this TaskRunnable is always empty
*/
public boolean isEmpty() {
return true;
}
/**
* Sets the TaskRunnable next to this TaskRunnable in the linked-list.
*
* @param task The next TaskRunnable
*/
public void setNext(TaskRunnable task) {
if (task == null) {
synchronized (this) {
if (parent != null) {
parent.trigger(time);
}
}
nextTask = null;
} else {
nextTask = task;
}
}
/**
* Implements for TaskRunnable interface, There is no previous element for
* HeadTaskRunnable.
*/
public void setPrevious(TaskRunnable task) {
}
/**
* Returns the TaskRunnable next to this TaskRunnable in the linked-list.
*
* @return next TaskRunnable object or null if it is not set
*/
public TaskRunnable next() {
return nextTask;
}
/**
* Implements for TaskRunnable interface, there is no previous element for
* HeadTaskRunnable.
*
* @return null means there is no previous element
*/
public TaskRunnable previous() {
return null;
}
/**
* Implements for TaskRunnable interface, HeadTaskRunnable doesn't have a
* run period.
*
* @return -1 means the task only will be run once
*/
public long getRunPeriod() {
return -1;
}
/**
* Implements for TaskRunnable interface.
*/
public void cancel() {
if (acquireValidLock()) {
try {
synchronized (this) {
if (parent != null) {
parent.trigger(time);
}
}
} finally {
releaseLockAndNotify();
}
}
}
/**
* Sets the Triggerable interface which will be run when the linked-list is
* empty.
*
* @param parent The Triggerable interface to be run when the linked-list is
* empty
*/
public void setTrigger(Triggerable parent) {
synchronized (this) {
this.parent = parent;
}
}
/**
* Sets the task which is the tail of the list.
*
* It is for internal use only.
*
* @param task The task which is at the tail of the list.
*/
public void setTail(TaskRunnable task) {
tailTask = task;
}
/**
* Returns the Task which is at the tail of the list.
*
* @return The task which is at the tail of the list.
*/
public TaskRunnable tail() {
return tailTask;
}
/**
* Returns the time which this HeadTaskRunnable is scheduled.
*
* @return The long value which represents the time this task is scheduled
*/
public long scheduledExecutionTime() {
if (expired) {
return -1;
} else {
return time.getTime();
}
}
/**
* Implements for TaskRunnable interface, just run the next TaskRunnable.
*/
public void run() {
TaskRunnable taskToRun = next();
do {
taskToRun.run();
} while ((taskToRun = taskToRun.next()) != null);
}
}